EFFECT OF FOLIAR APPLIED NITROGEN AND POTASSIUM ON COTTON IN THE SAN JOAQUIN VALLEY OF CALIFORNIA
Mar 10, 2017

Agronomy & physiology WCRC Agro-Physio-north-america WCRC1
Abstract                                                                         Back to Table of contents

Improved cotton varieties and improved cultural practices have caused lint cotton yields to improve at a rate of 36 kg ha-1 year-1 over the past ten years. Earlier maturing varieties, 76 cm rows, better irrigation regimes, improved pest management, and the wide spread use of plant growth regulators, have all had a part in the yield increases. Since bolls are strong sinks for nitrogen and potassium, these nutrients are needed in even larger quantities during boll development. Foliar applications of nitrogen in conjunction with pix (mepiquat chloride) resulted in increased yields even when it was thought that soil levels were adequate.

Timing of foliar potassium in five tests in two years, showed that two to three weeks after first bloom was the best time for applications. Potassium applied prior to two weeks after first bloom or later in the season resulted in less yield response. There was no difference between the effects of potassium nitrate or potassium sulfate when used as a foliar potassium spray.

Conclusions

The results of these tests show that benefits can be obtained from foliar applications of nitrogen and potassium. New, more determinant cotton varieties which set the crop over a short period of time, require larger amounts of some nutrients during this critical stage of development. Determinant varieties coupled with cultural practices which push the crop toward earlier termination cause need for supplemental nitrogen and potassium to be even greater. Even though the soil nitrogen and potassium levels were adequate according to cotton fertility guidelines, foliar applications of these nutrients at two to three weeks after first bloom caused positive yields responses.

It should be emphasized that foliar applications are by no means a substitute for sound fertilizer practices, and, if used, should only be supplemental.

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